1. Technical Field
The present invention relates to a flame-retardant composition that is preferably used as a covering material of a covered electric wire that is preferably used for wiring of parts for a car and parts for an electrical/electronic appliance, and a covered electric wire and a wiring harness using the same.
2. Background Art
A variety of properties such as mechanical properties, flame retardancy, heat resistance, and cold resistance are required of an insulated material that is preferably used for parts for a car such as an automobile and parts for an electrical/electronic appliance according to the intended use. Conventionally, for the insulated material, a material that is prepared by blending a polyvinyl chloride resin compound and a halogenous flame retardant containing a halogen atom is often used.
From the view point of reducing loads on the global environment, a non-halogenous material such as an olefin polymer that does not emit harmful halogenous gas during combustion has been recently used. In a material that does not have flame retardancy in itself such as the olefin polymer, a flame retardant is blended therewith in order to impart flame retardancy. Examples of the flame retardant containing no halogen atom include metal hydroxide such as magnesium hydroxide.
Examples of the magnesium hydroxide include magnesium hydroxide derived from magnesium in sea water and magnesium hydroxide derived from a natural mineral. Among them, the magnesium hydroxide derived from the natural mineral is comparatively reasonable in price, and therefore, a pulverized natural mineral containing magnesium hydroxide as the main ingredient is sometimes used as the flame retardant.
For example, Patent Literature 1, JP 3280099, discloses a flame-retardant composition that is prepared by blending a plastic or a rubber and a pulverized natural mineral containing magnesium hydroxide as the main ingredient that is a flame retardant.
However, when the pulverized natural mineral containing the magnesium hydroxide as the main ingredient is used as the flame retardant, the flame-retardant composition is sometimes colored in red during compounding or molding of the flame-retardant composition. The reason why the flame-retardant composition is colored as such was not known well.
For example, a covering material for a covered electric wire is sometimes provided with printing of letters and coloring for color coding in order to identify the kind of the electric wire. Thus, if the flame-retardant composition is colored despite the intention, printed characters are hard to see, or desired color coding cannot be performed. As a result, the identification of the electric wire could not be performed.
An object of the present invention is to provide a flame-retardant composition that is not colored during compounding or molding, and a covered electric wire and a wiring harness using the same.